First topic. Mr. Miner’s first-hand experience and knowledge about cement/plaster hydration (hardening) issues provides some key and valid points about this topic. Interestingly, he had to explain to a plaster contractor that using a low water/cement ratio and adding minimal calcium chloride to plaster mixes would help reduce “cracking and shrinkage” problems that had been noticed in some prior pools. It is also well-known that high heat and dry conditions can also lead to excess shrinkage.
Why is the only solution considered to resolve shrinkage problems is to start filling the pool immediately? What about the shallow-end steps that don’t receive water for at least 24-48 hours? Or that many plasterers wait for a day to fill the pool after they have removed some cement and exposed the quartz or pebble aggregate? How can waiting a few hours to start filling be bad when waiting a day doesn’t? Those are conflicting and nonsense positions. Additionally, why hasn’t the plaster contractor also thought of “tenting” the pool after finishing to protect it from the hot sun?
Let me suggest why. Because the NPC doesn’t educate their plaster members about proper plastering workmanship and practices. They have no guidelines, standards, or limits on water content, calcium chloride, water troweling, and protecting plaster from hot and dry temperatures. Instead, their literature suggests that virtually every plaster problem is caused by slightly aggressive water.
I do not understand how can anyone would consider the NPC organization, their literature, and their claims as being credible when they disregard all literature and documented studies, especially from the ACI and PCA regarding what is required for the cement’s structural integrity? When confronted with known and established science regarding improper materials and workmanship, the NPC tries to suggest that pool plaster is vastly different from cement/concrete sidewalks. They ignore that both pool plaster and concrete contains a significant amount of Portland cement. It is the cement, and only that product, that undergoes hydration, and is affected by the water content, calcium chloride additions, and water troweling, late hard troweling, and yes, early filling. The aggregate, whether it is calcite, marble, quartz, or pebble is not a player or affected by hydration and curing issues. Simply put, plaster and concrete react similarly when subjected to improper mixing and troweling conditions.
Second topic. I cringe when some people advise homeowners to rely upon a plaster company’s warranty for plaster workmanship because it is vastly different from warranties for a TV or computer. If something goes wrong with those items, then they provide a new part or a brand new one. That restores to the purchaser what he originally paid for. But not so with new pool plaster.
When poor workmanship is performed and causes a discoloration, the plasterer will often suggest a remedy such as, an acid treatment, a torching process, a patching job, or sanding and polishing to remove the discoloration. Unfortunately, every one of those treatments are detrimental to the plaster finish and they age the plaster and reduce the life of the plaster finish dramatically. To a plastering contractor, those remedies are somewhat inexpensive and often do not work. Yet, they usually walk away and refuse any further warranty work. After that? It means that the pool will need re-plastering much sooner than usual. Not a bad deal for them if they refuse to be held responsible!
Even if the contractor agrees to re-plaster the pool, they usually charge extra for something, AND, a re-plastering job also has it own potential problems with bonding and cracking issues. That also means a likelihood that another re-plastering job sooner than later. It seems to me that the NPC has figured out a way to generate increased revenue for its’ members.
I would try anything to prevent bad workmanship in the first place. Warranties don’t guarantee.